Messages

1

Mach4 General Discussion / Re: 2.5 carving - Z stepper creeping upward

« on: October 29, 2017, 04:01:17 PM »

Thanks everyone for the help.  We have loved just about everything about Mach 4 and the pmdx - literally the only thing that I thought I'd add to improve is an undo button for the tool offset dialogue box (sometimes you accidentally click input + instead of input).  It's been a great program.

For some reason we couldn't get the other steppers we had to hold position?  We still dont understand why.  In any event the problem was solved with the new motors and a setting change.

Thanks everyone for your feedback; it has been a great help!

2

Mach4 General Discussion / Re: 2.5 carving - Z stepper creeping upward

« on: October 29, 2017, 12:46:33 PM »

Looks like we may have just solved it.  We switched motor settings back to active low instead of active high.  (Simple enough)

A little history:  with the first budget steppers we had we had this issue either way - in fact, if I remember right, active high ran better than active low, but it still creeped up throughout the course of the cycle.

With the installation of these new clear paths, we didn't think to change it back until this morning.  For whatever reason that seems to have solved the issue.  I set up a few different contour/relief carve cycles and it's holding position perfectly now.

...and there was much rejoicing...

3

Mach4 General Discussion / Re: 2.5 carving - Z stepper creeping upward

« on: October 29, 2017, 12:58:45 AM »

Well we fixed the VFD issue (I believe the only change my dad made was the installation of a relay for vfd run terminal?).  Thanks very much for help there.  Something someone said tipped my pa' off though.  Spindle is no longer an issue.

The z creeping issue remains though.  He did mess with active high/low signal polarity and made sure requirements were matched.  

He did  reduce acceleration to see if that would help; and I think it may have helped a small amount?  The issue was still there though..

We tried everything with the basic steppers we had.  We had been considering  changing our our steppers with clear path motors:

https://www.teknic.com/products/clearpath-brushless-dc-servo-motors/clearpath-sd-stepper-replacement/

So we went ahead and did that today- I love these new motors (they are much faster and much more quiet, and they eliminated the need for the other stepper drivers we had mounted in our controls box), but to our dismay the exact same problem is still there, even with these servos.  We are still creeping upward in Z when relief carving.

It did not matter if we ran it at 75ipm or 175ipm.  We slowed down acceleration and it did not remove the problem....just...nothing worked.

At least we know it's not the motors or drivers now.  

Im a big layman here, so I apologize for sounding so crude in describing all this; it seems to me at this point that it's either the PMDX, Mach 4, our PC or something I'm doing wrong in outputting g code from artcam.  Either some Mach 4 setting we have wrong (but I'm told my father has tried seemingly everything), or maybe a computer/USB that isn't capable of feeding voltage signals to PMDX?  or .....something... I don't know what.  

We were thinking about trying to switch PCs out (our current one is a cheapee Lenovo touch screen) but I don't believe Mach 4 will  let you install on more than one comp; so we have to wait until Monday to contact them.

Wish I understood all of this a little better.  

Thanks again for the help.

4

Mach4 General Discussion / 2.5 carving - Z stepper creeping upward

« on: October 01, 2017, 08:10:08 AM »

So my father and I designed and built our own 2' x 4' cnc router:

http://www.openbuilds.com/builds/warnke-cnc-router.4383

All seemed to be well until we began to try our hand at a complex relief carving:

http://www.openbuilds.com/threads/suggestions-to-streamline-my-router-motors.10184/#post-58655

We are seeing an issue in the z motor where it gradually loses position as it works its way through the carving.  It is creeping upward (not downward) and it is a gradual consistent position loss - about .005" loss of position in z (shift upward) per 16" by 1" of carved area.

Some pertinent specs on all of this:

We are generating g code using an stl in artcam.  G code looks fine.
We are using Mach 4 as our router software.  
We have the PMDX-424 for our motion controller

http://www.pmdx.com/PMDX-424

Here is what we purchased for motors drivers and power supplies (these exact ones from this site, tho we added 1 more set to our order as we have a dual driven y axis and we intend to add a rotary axis later; so 5 motors total):

https://www.omc-stepperonline.com/cnc-kit/4-axis-85ncm1204ozin-nema-34-stepper-motor-and-driver-and-power-supply-4-ma860h-34hs46.html

We have tried a lot of different parameter changes, switching voltage settings, slowing everything way down, etc and nothing seems to make a difference.  It's just not holding position in z when it cuts this relief carving.

We did a test cycle where we just moved the z motor straight  up and down in repetition a bunch for a prolonged period of time and it held position.  It only seems to lose position when carving stuff like this.

The coupling is not lose at all (we double set screwed each side to each shaft - plus that wouldn't account for consistent z position loss upward anyway).

We are running a windows 10 PC USB'd to our PMDX board.

At this point we pretty much figure the problem is either Mach 4, the pmdx motion controller or the motor driver...I guess it could be the computer or USB? I don't know.

To add to the frustration, after a week of running great (beside the position loss) now when you tell our VFD air cooled motor to turn off in Mach 4, it doesn't stop right away...it just keeps going and gradually slows down whenever it wants bit by bit (sometimes not at all and you have to turn power off)..

Neither of us are electricians or controls guys.  We are machinists and mechanical designers, but the controls stuff was a first try rookie effort so it's a little frustrating stumbling around this all.  We just want everything to work like we need it to.

Any ideas on what this could be?  

Does anyone else run Mach 4 with the PMDX?  Anyone else see these issues?  Position loss in z or spindle not turning off when you push the spindle off button in Mach 4? (Spindle on button is working fine).


Thanks for any help.  We keep trying things to no avail and we are starting to get discouraged  here!